The desorption of organic substances in a regenerative operating adsorption plant is usually obtained by hot-gas or water-vapor desorption. Since the input of energy is related to volumetric flow, a concentrating of the desorbate is possible only to a limited extent. This process is not very efficient, particularly for hot-gas desorption, since the heat capacity of air is small, and the heat transfer between air and adsorption agent is unfavorable. For decreasing concentrations of pollutants, the energy requirement per unit quantity of separated pollutant increases. An energy justifiable operation of such a plant it thus only conditionally possible.
Since polar molecules, particularly water, absorb microwave energy, it is known to evaporate water with microwave energy. Other polar organic compounds, such as alcohols, which are adsorbed on an adsorption agent can be evaporated by microwave energy in order to regenerate the adsorption agent. Less polar or even nonpolar organic compounds, however, cannot be removed in this way. A number of nonpolar or less polar pollutants are, however, contained in the air, and these are adsorbed by the adsorption agent and thus must be desorbed again in order to regenerate the adsorption agent.
Nonpolar compounds in the air, are, for example, alkanes or other aliphatic hydrocarbons and aromatic hydrocarbons, such as, benzene.